The present invention relates to a selector valve with a magnetometric sensor for detecting an operating position of a spool by using a magnet and a magnetometric sensor.
There is a known selector valve with a magnetometric sensor in which switching operation of a spool can be detected by providing a magnet and the magnetometric sensor as disclosed in Japanese Utility Model Application Laid-open No. 2-66784, for example. This known selector valve is formed by mounting the magnet to an outer periphery of the spool and mounting the magnetometric sensor to a casing. When the spool moves to one switching position, the magnet approaches the magnetometric sensor and the magnetometric sensor is turned on. When the spool moves to the other switching position, the magnet is separated from the magnetometric sensor and the magnetometric sensor is turned off. Switching of the spool is detected by turning on and off of the magnetometric sensor.
However, because the magnet is mounted to a central portion of the spool sliding in a valve hole and the magnetometric sensor is mounted to a central portion of the casing corresponding to the magnet in the prior-art selector valve, special spool and casing with complicated structures different from those of a selector valve without a magnetometric sensor have to be used. Especially in a case of the casing, because a plurality of ports, a plurality of flow paths connecting the ports and the valve hole, or a plurality of pilot flow paths are normally formed in a complicated state, it is extremely difficult in terms of design to newly provide a mounting hole in which the magnetometric sensor is to be mounted, an introducing hole for wiring, and the like while preventing them from interfering with the ports and flow paths. Therefore, in order to simplify the structure, it is preferable to use as many parts as possible in common with the normal selector valve without the magnetometric sensor. It is especially desirable to use the common casing.
Furthermore, in order to precisely control operation of the selector valve and to predict a failure, it is preferable to detect not only if the spool has reached a stroke end but also every operating position of the spool by using the magnet and the magnetometric sensor.
It is a main technical object of the present invention to provide a selector valve with a magnetometric sensor, the selector valve being able to be formed easily by using a casing in common with a normal selector valve without a magnetometric sensor, a structure of the selector valve being simple, and the selector valve being able to be produced easily.
It is subsidiary another technical object of the invention to form the above-described selector valve with the magnetometric sensor such that an operating position of a spool can be detected throughout a stroke.
To achieve the above objects, a selector valve of the present invention comprises: a casing having a plurality of ports and a valve hole into which the ports open; a spool housed for sliding in the valve hole and having one end extending outside from the valve hole to switch flow paths; end blocks mounted to opposite sides of the casing; driving means for driving the spool; a magnet mounted to a portion of the one end of the spool extending from the valve hole so as to move with the spool outside the valve hole; a detecting block disposed between one end of the casing and one of the end blocks so as to surround the magnet mounted to the spool; and at least one magnetometric sensor mounted to the detecting block so as to be able to detect magnetism from the magnet.
According to the selector valve with the magnetometric sensor of the invention having the above structure, by disposing the detecting block between the casing and the end block, mounting the magnetometric sensor to the detecting block, causing the end portion of the spool to extend into the detecting block, and mounting the magnet to the extending portion, as compared with a normal selector valve without the magnetometric sensor, it is unnecessary to subject the casing having a complicated structure to any special processing and it is possible to easily form the selector valve with the magnetometric sensor by using the casing in common with the normal selector valve by only and newly preparing the detecting block and making few improvements to the spool.
According to a preferable concrete embodiment of the invention, the detecting block includes a first portion sandwiched between the casing and the end block to surround an area where the magnet moves and a second portion positioned along an outer face of the selector valve astride the first portion and the end block, a sensor mounting groove is formed in the second portion in parallel with an axis of the spool and astride the moving area of the magnet, and the magnetometric sensor is fitted in the sensor mounting groove.
In this case, it is preferable that the magnetometric sensor is mounted in the sensor mounting groove so as to be able to detect the magnetism from the magnet throughout a stroke of the spool and that every operating position of the spool can be detected from a change in magnetic flux density due to movement of the magnet.
As a result, because not only positions of the spool at the stroke ends but also a position at any midpoint of the stroke can be detected, it is possible to easily judge by a judging circuit if the spool has operated normally from a relationship between positions and operating time of the spool from start to finish of the stroke. Thus, it is possible to take preventive measures prior to a failure and to prevent suspension of operation of an operating system for many hours due to the failure and an accident.
According to another concrete embodiment of the invention, the driving means is a solenoid-operated pilot valve, the spool is switched by one or two pilot valve(s), every pilot valve is mounted to one of the end blocks, and the magnet and the magnetometric sensor are provided on a side of the end blocks to which the pilot valve(s) is(are) not mounted.